This week on Table Talk we are focusing on the topic of lamb survival
- First post: importance of lamb survival for our businesses and our industry and how to calculate lamb survival $
- Second post: improving lamb survival through managing ewe condition
In the final post for the week, we are considering the influence of genetics on lamb survivability. The estimated loss of perinatal lamb loss to the industry if $56 million (Nuffield Scholar, Matthew Ipsen), therefore the ability to select sheep with a genetic propensity towards lamb survival would be an incredibly desirable one for producers and the wider industry.
Matching rams to ewes is critical and having a clear breeding objective frames this joining decision. Nuffield Scholar, Matthew Ipsen, stated that world’s best practice management in lamb survival focused on:
- Select rams on ASBVs for total weaning weight
- Identifying and retaining the best performing uses and removing the worst performed (selection intensity)
But, what about the possibility of improving lamb survival through selecting for maternal traits in ewes?
A Swedish research paper reviewed the possible genetic gain of including traits for maternal behaviour in sheep breeding programs as a mean to improve lamb survival. A measurement used in the literature for maternal behaviour is MBS (maternal behaviour score), which measures the distance between ewe and lamb during handling of the lamb. They found heritability and repeatability for maternal behaviour score (MBS) were low to moderate and correlations with litter survival were also low. Modest genetic gain in selecting for MBS is to be expected but the progress will be slow.
Australian research focused on how we can improve lamb survival through genetic temperament traits in Merino ewes. The researchers stated that if a relationship between temperament and lamb survival could be established, then we may be able to use indirect selection to enable an increased gain in lamb survival. The researchers stated that if a relationship between temperament and lamb survival could be established, then we may be able to use indirect selection to enable an increased gain in lamb survival. Improving lamb survival through indirect selection for temperament may be unlikely. However, the results did show temperament traits were low to moderately heritable and therefore can be suitable for use in genetic selection.
Research from New Zealand investigated the genetic effects on lamb survival and mortality traits on easy care sheep farms. The flocks included a range of breeds (36% Romney, 7% Perendale, 4% Coopworth, and 2% Texel) and their crosses (2 breed combinations; 11%) and composites (defined as a combination of 3 or more breeds; 35%; Price, 2000). They found lamb survival heritabilities reported are very low.
Sue Hatcher and Elhan Safari analysed over 14,000 lambs born between 1975 and 1983. The results suggested indicated that lamb survival beyond the first week of birth is largely beyond the control of the ewe. Overall, the study found:
- Very low heritability for lamb viability (0.03)
- Very low heritability for the performance of the dam or ewe rearing ability (0.07)
They stated that culling ewes that have a poor rearing ability can improve current generation improvement. Despite the repeatability and moderately heritable nature of maternal bond score and lamb birth weight, the correlation with lamb survival was basically zero. As a result, the traits should not be used as an indirect selection criteria for merino lamb survival.
Therefore, the research to date has shown low to moderate linkages between maternal traits and lamb survivability. We recommend looking back at our second post that focuses on management techniques to improve lamb survivability.
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